PD-97509
IR3843AMPbF
SupIRBuck
Features
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TM
HIGHLY EFFICIENT
Description
The IR3843A
SupIRBuck
TM
is an easy-to-use,
fully integrated and highly efficient DC/DC
synchronous Buck regulator. The MOSFETs co-
packaged with the on-chip PWM controller make
IR3843A a space-efficient solution, providing
accurate power delivery for low output voltage
applications.
IR3843A is a versatile regulator which offers
programmability of start up time, switching
frequency and current limit while operating in
wide input and output voltage range.
The switching frequency is programmable from
250kHz to 1.2MHz for an optimum solution.
It also features important protection functions,
such as Pre-Bias startup, hiccup current limit and
thermal shutdown to give required system level
security in the event of fault conditions.
INTEGRATED 3A SYNCHRONOUS BUCK REGULATOR
Wide Input Voltage Range 1.5V to 21V
Wide Output Voltage Range 0.7V to 0.9*Vin
Continuous 3A Load Capability
Integrated Bootstrap-diode
High Bandwidth E/A for excellent transient
performance
Programmable Switching Frequency up to 1.2MHz
Programmable Over Current Protection
PGood output
Hiccup Current Limit
Precision Reference Voltage (0.7V, +/-1%)
Programmable Soft-Start
Enable Input with Voltage Monitoring Capability
Enhanced Pre-Bias Start-up
Seq input for Tracking applications
-40
o
C to 125
o
C operating junction temperature
Thermal Protection
Multiple current ratings in pin compatible footprint
5mm x 6mm Power QFN Package, 0.9 mm height
Lead-free, halogen-free and RoHS compliant
Applications
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Server Applications
Storage Applications
Embedded Telecom Systems
Distributed Point of Load Power Architectures
1.5V <Vin<16V
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Netcom Applications
Computing Peripheral Voltage Regulators
General DC-DC Converters
4.5V <Vcc<5.5V
Seq
Vcc
PGood
PGood
Enable
Vin
Boot
Vo
SW
OCSet
Fb
Rt
Comp
SS/ SD
Gnd
PGnd
Fig. 1. Typical application diagram
Rev 16.0
1
PD-97509
IR3843AMPbF
ABSOLUTE MAXIMUM RATINGS
(Voltages referenced to GND unless otherwise specified)
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Vin ……………………………………………………. -0.3V to 25V
Vcc ……………….….…………….……..……….…… -0.3V to 8V
(Note2)
Boot
SW
……………………………………..……….…. -0.3V to 33V
…………………………………………..……… -0.3V to 25V(DC), -4V to 25V(AC, 100ns)
……..…………………………….…..….. -0.3V to Vcc+0.3V
(Note1)
Boot to SW
OCSet
………………………………………….……. -0.3V to 30V, 30mA
……………………………….. ... -0.3V to Vcc+0.3V
(Note1)
Input / output Pins
PGND to GND ……………...………………………….. -0.3V to +0.3V
Storage Temperature Range ................................... -55°C To 150°C
Junction Temperature Range ................................... -40°C To 150°C
(Note2)
ESD Classification …………………………… ……… JEDEC Class 1C
Moisture sensitivity level………………...………………JEDEC Level 2@260 °C
(Note5)
Note1:
Must not exceed 8V
Note2:
Vcc must not exceed 7.5V for Junction Temperature between -10
o
C and -40
o
C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the
device. These are stress ratings only and functional operation of the device at these or any other
conditions beyond those indicated in the operational sections of the specifications are not implied.
PACKAGE INFORMATION
5mm x 6mm POWER QFN
SW
V
IN
12
11
10
PGnd
θ
JA
=
35
o
C / W
θ
J
-
PCB
=
2
o
C / W
Boot
Enable
13
14
1
2
3
15
Gnd
9
8
V
CC
PGood
4
5
6
7
ORDERING INFORMATION
PACKAGE
DESIGNATOR
M
M
Rev 16.0
Seq
FB COMP Gnd Rt
SS OCSet
PACKAGE
DESCRIPTION
IR3843AMTRPbF
IR3843AMTR1PbF
PIN
COUNT
15
15
PARTS PER
REEL
4000
750
2
PD-97509
IR3843AMPbF
Block Diagram
Fig. 2. Simplified block diagram of the IR3843A
Rev 16.0
3
PD-97509
IR3843AMPbF
Pin Description
Pin
1
2
3
4
5
Name
Seq
Fb
Comp
Gnd
Rt
Description
Sequence pin. Use two external resistors to set Simultaneous Power up
sequencing. If this pin is not used connect to Vcc.
Inverting input to the error amplifier. This pin is connected directly to the
output of the regulator via resistor divider to set the output voltage and
provide feedback to the error amplifier.
Output of error amplifier. An external resistor and capacitor network is
typically connected from this pin to Fb pin to provide loop
compensation.
Signal ground for internal reference and control circuitry.
Set the switching frequency. Connect an external resistor from this pin
to Gnd to set the switching frequency.
Soft start / shutdown. This pin provides user programmable soft-start
function. Connect an external capacitor from this pin to Gnd to set the
start up time of the output voltage. The converter can be shutdown by
pulling this pin below 0.3V.
Current limit set point. A resistor from this pin to SW pin will set the
current limit threshold.
Power Good status pin. Output is open drain. Connect a pull up resistor
from this pin to Vcc. If unused, it can be left open.
This pin powers the internal IC and the drivers. A minimum of 1uF high
frequency capacitor must be connected from this pin to the power
ground (PGnd).
Power Ground. This pin serves as a separated ground for the MOSFET
drivers and should be connected to the system’s power ground plane.
Switch node. This pin is connected to the output inductor.
6
SS/SD
¯¯
7
8
9
10
11
OCSet
PGood
V
CC
PGnd
SW
V
IN
Boot
Enable
Gnd
12
13
14
15
Input voltage connection pin.
Supply voltage for high side driver. A 0.1uF capacitor must be
connected from this pin to SW.
Enable pin to turn on and off the device. Use two external resistors to
set the turn on threshold (see Enable section). Connect this pin to Vcc if
it is not used.
Signal ground for internal reference and control circuitry.
Rev 16.0
4
PD-97509
IR3843AMPbF
Recommended Operating Conditions
Symbol
V
in
V
cc
Boot to SW
V
o
I
o
Fs
T
j
Definition
Input Voltage
Supply Voltage
Supply Voltage
Output Voltage
Output Current
Switching Frequency
Junction Temperature
Min
1.5
4.5
4.5
0.7
0
225
-40
Max
21*
5.5
5.5
0.9*Vin
3
1320
125
Units
V
A
kHz
o
C
*
SW must not exceed the Abs Max Rating (25V)
Electrical Specifications
Unless otherwise specified, these specification apply over 4.5V< V
cc
<5.5V, V
in
=12V, 0
o
C<T
j
< 125
o
C.
Typical values are specified at T
a
= 25
o
C.
Parameter
Power Loss
Power Loss
P
loss
Vcc=5V, V
in
=12V, V
o
=1.8V, I
o
=3A,
Fs=600kHz, L=2.2uH,
Note4
0.682
W
Symbol
Test Condition
Min
TYP
MAX
Units
MOSFET R
ds(on)
Top Switch
Bottom Switch
R
ds(on)_Top
R
ds(on)_Bot
V
Boo t
-V
sw
=5V, I
D
=3A, Tj=
25 C
V
cc
=5V, I
D
=3A, Tj=
25 C
o
o
24.5
24.5
32
32
mΩ
Reference Voltage
Feedback Voltage
Accuracy
V
FB
0
o
C<Tj<125
o
C
-40 C<Tj<125 C,
Note3
o
o
0.7
-1.0
-2.0
+1.0
V
%
+2.0
Supply Current
V
CC
Supply Current (Standby)
V
cc
Supply Current (Dyn)
I
CC(Standby)
I
CC(Dyn)
SS=0V, No Switching, Enable low
SS=3V, Vcc=5V, Fs=500kHz
Enable high
10
500
μA
mA
Under Voltage Lockout
V
CC
-Start-Threshold
V
CC
-Stop-Threshold
Enable-Start-Threshold
Enable-Stop-Threshold
Enable leakage current
V
CC
_UVLO_Start
V
CC
_UVLO_Stop
Enable_UVLO_Start
Enable_UVLO_Stop
Ien
Vcc Rising Trip Level
Vcc Falling Trip Level
Supply ramping up
Supply ramping down
Enable=3.3V
3.95
3.65
1.14
0.9
4.15
3.85
1.2
1.0
4.35
4.05
1.36
1.06
15
V
μA
Rev 16.0
5
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